Control system for pipe organs



June 23, 1964 A. R. RIENSTRA 3,138,053

CONTROL SYSTEM FOR PIPE ORGANS Filed July 6, 1960 2 SheetsSheet 1 PIPE 77 INVENTOR. ALBERT R. RIENsv-RA ATTORNEYS.

June 23, 1964 R. RIENSTRA 3,138,053

CONTROL SYSTEM FOR PIPE ORGANS Filed July 6, 1960 2 Sheets-Sheet 2 A INVEN TOR.

ALBERT R fP/EMSTRA ATTORNEYS- United States Patent 3,138,053 CONTROL SYSTEM FOR PIPE ORGANS Albert R. Rienslra, Dogwood Drive, Rte. 17, Morristown, NJ. Filed July 6, 1960, Ser. No. 41,184 9 Claims. (Cl. 84-338) This invention relates to control systems for musical instruments and more particularly to control systems for controlling the sound sources of an instrument, for example the pipes of an organ. While the invention will be described in terms of its application to organs, it should be understood that it is also applicable in analogous fashion to other musical instruments.

In their rudimentary form pipe organs provide for direct control of the pipes from the keys through a mechanical linkage. Operation of the keys through this linkage serves to open and close valves which control the sounding of the pipes. With such an arrangement there arises the need to keep the console in close proximity with the organ; linkages for remote transmission of key actions are beset by considerable practical difiiculties. The proximity of the console to the organ engenders several resultant disadvantages: Being close to the instrument the organist is in general not in a suitable position to direct the choir. Further, close proximity to the organ does not provide the organist with an opportunity to hear the organ sounds as they are intended to be heard nor as they are heard by the audience at large. This lack of proper sound perspective adds burdens to an already demanding task.

In order to overcome the aforementioned disadvantages the art has developed systems for remotely controlling the organ by the use of electrical techniques. To this end, prior arrangements provide means for converting key action into an electrical signal; the signal is then transmitted via wires to the organ where it is used to operate an electro-magnetic device which operates, in turn, either pneumatically or directly, the associated pipe valve or valves. While this system enables remote operation of the instrument, it introduces a defect not known With the mechanical action, i.e., the conventional tracker-type of control, first described. Unlike the basic system where the player controls the position and rate of movement of the pipe valves, thereby controlling transients, the remotely operated electrical system deprives the organist of control over both valve speed and valve position. The valve-actuated magnetic device in the latter arrangement has a transient velocity response which is fixed and independent to the rate of depression of the actuating key. Moreover, partial opening and closing of the valves is not possible since the electro-magnetic actuator employed in these arrangements has but two stable states, full open and full closed. It is accordingly not possible to partially open a valve because once the magnet is actuated its armature will drive to the completely energized state, thus fully opening or closing the valve, as the case may be. Even if a magnetic actuator with a controllable transient were employed in the known arrangements, the organist would still lack control over the sound transients because the mechanism for converting key action into an electrical signal also has but two stable states, On and Off. In other words, the key when depressed generates a fixed amplitude signal which energizes the magnet; alternatively, the signal is attenuated to zero and the magnet released when the key is released. Intermediate key positions are accordingly not translated or sensed, so that both the input and output ends of the known system are devoid of true controllable position characteristics. Lacking these they are also devoid of controllable speed or velocity characteristics.

It is accordingly an object of the invention to provide 3,,l33fi53 Patented June 23, 1964 a control system for controlling the sound sources of a musical instrument from the associated keys, said system being responsive to the degree and rate of displacement of said keys.

A further object of the invention is to provide a control system for musical instruments whereby an electrical signal is generated according to the degree of displacement of the playing keys, the signal being employed to energize an actuator for the sound sources of the instrument. The actuator is continuously adjustable so that it has at least three and more generally, an infinite number of stable states.

A still further object of the invention is to provide means for controlling the sound sources of a musical instrument and particularly means for enabling the musician to control the transient actions associated with energizing and denergizing the sound sources.

An additional object of the invention is to provide a. control system for musical instruments wherein the musician may be located remotely from the sound sources of the instrument, and wherein a response to both the degree of displacement and rate of the displacement of the playing keys is obtained.

A further object of the invention is to provide an electrical actuator for controlling pipes in an organ and the like, the actuator being responsive in velocity and degree of actuation to the actuation of the playing keys.

These and other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

Briefly and generally the system according to the invention comprises means coupled to the playing keys for converting displacement of the same into related electrical signals. These signals are coupled to an output transducer or actuator which reconverts the signals into related mechanical displacements. These displacements are operatively coupled to the control mechanisms which control the issuance of sound from the instrument. The invention also contemplates a special actuating device which is controllable both as to position and velocity of movement.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

Serving to illustrate exemplary embodiments of the invention are the drawings of which:

FIGURE 1 is a schematic illustration of the overall system of the invention.

FIGURE 1a is a detail of FIGURE 1 taken along the lines 1A-1A thereof and enlarged;

FIGURES 2, 3 and 4 are elevation views partly in section and partly diagrammatic illustrating various actuator arrangements for controlling the sounding of organ pipes and the like;

FIGURES 5 to 8 are schematic diagrams representing various arrangements for converting key displacements into corresponding electrical signals; and

FIGURE 9 is an elevation view partly in section and partly diagrammatic of a system for controlling an organ pipe or set of pipes from the associated key with the aid of a multi-position switch and multi-position solenoid.

In FIGURE 1 there i illustrated the ba i elements of the control system by which key 10 controls pipe 11, the latter being mounted in a wind chest according to typical pipe organ arrangements. For controlling pipe 11, the movement of key 10 is coupled to a key transducer system which converts these key movements into corresponding electrical signals. These signals are transmitted by a circuit 13 to an electro-magnetic actuator 14, which includes an axial pole 14a around which a coil is wound. Cooperating with pole 14a is armature 14b of conventient L shape with the horizontal portion being preferably oriented approximately parallel to the coil axis and pole. The armature is pivoted at the free end of the horizontal section to bracket 15 by way of pivot pin 16. Certain relationships between the armature and the pole which govern the formers response will be described hereinafter. The actuator 14 at its rear is also secured to this bracket by screw 14d or other convenient mounting means. Armature 14b is normally held in the retracted position by spring 13 connected to the central horizontal section of the armature and to a transverse flange of bracket 15. This flange is secured to a convenient frame section of the instrument.

Upon actuation of key 10, electrical signals are generated in the key transducer system and are coupled via circuit 13 to the coil of actuator 14. Energization of the coil causes armature 14b to be attracted toward pole 1411 about pivot 16, the extent of travel being dependent on the degree of energization. This resultant motion of the armature is transmitted to the wind chest as symbolically indicated at 17 for controlling pipe 11. For limiting the travel of the armature and for damping the noise associated with limiting, a damped stop 19 of felt or similar material is provided, this stop being connected to the armature 14b and positioned to engage tongue 19' on bracket 15 after the armature has moved through a predetermined distance.

The characteristics of actuator 14 are such that the position of the armature and the speed of movement thereof are controlled according to the amplitude of the energizing signal transmitted over circuit 13. These characteristics are in marked contrast to typical magnetic arrangements wherein actuation of the coil structure triggers an uncontrolled action which results in the armature being more or less attracted rapidly into the full On position.

The electro-magnetic actuator according to the invention has a velocity response and position response controllable according to the energizing signal by virtue of several factors including special contouring of the armature and/ or pole piece. Thus, there is provided a groove 140 in armature 1415 (FIGURE 1a) and a concave contour in the face of pole piece 14a, they being shaped such that the air gap between the pole piece 14a and the armature 14b increases as the armature is attracted. By this arrangement the usual rapid and unstable travel of the armature to its limit is avoided and the position of the armature and its rate of change of position are controllable according to the degree of energization of the actuator field. Thus, if the musician displaces the key to an intermediate position, armature 14b assumes a corresponding intermediate position. If the musician depresses the key at a rapid rate the armature 14b similarly moves at a rapid rate. Accordingly, the mechanical actuation of the valves in the wind chest which control pipe 11 is more nearly representative of the manner in which the musician has operated the keys. In this way transient tone generation and decay are placed under the control of the organist, thus providing for improved quality of the music.

Serving to complement the contouring of the armature or serving as an alternative technique, is the adjustment of the are traced by the armature 14b relative to the arc of pole piece 14a. These may be adjusted relative to one another so that the effective air gap between the armature and pole piece is larger, the same as, or smaller when the armature is fully attracted than when it is in its deenergized position. By suitable regulation of these arcs and/ or the geometry of the armature contour, the static and dynamic reluctance of the magnetic path can be adjusted and the transient action of the armature can be 4 accordingly adjusted to provide various force-versus-armature travel characteristics. These characteristics can be controlled to provide a constant attractive force over the entire travel, a decreasing or increasing force as travel progresses or even a notched characteristic having both increasing and decreasing force intervals.

Actual mechanisms for controlling the pipes are illustrated in FIGURES 2, 3 and 4. In FIGURE 2 pipes 22 are mounted on pipe chamber 21 and communicate with the interior thereof through passageways 22a. Control over the aperture of these passageways is provided by sliders 23 operated by suitable stops, not shown. Adjoining chamber 21 is wind chest 20 separated therefrom by inclined partition 45 which includes a port 41 for providing communication between the chest and chamber. Cooperating with port 41 is a valve 42 on the face of which a compliant pad 42a is provided. Valve 42 is attached to an intermediate point of armature 14b. The latter is pivoted at one end on a bracket 15 which is attached to partition 45 by screws 15a, the bracket being transverse with respect to the partition. Also mounted on the bracket 15 is the field or stator of magnetic actuator 14, the stator and its pole face 14a being oriented in spaced, approximately parallel relation to the armature as described in connection with FIGURE 1. It may be seen from FIGURE 2 that the need for a spring such as 18 of FIGURE 1 is eliminated, gravity being relied on to restore the armature.

When energized by key displacements, actuator 14 attracts armature 14b, and the latter tracks the key displacements, assuming a position determined by the degree of displacement at a rate controlled according to the rate of displacement. Valve 41 responds accordingly. The sounding of pipes 22 including the transient actions thereof are thus controlled by operation of the associated key.

In FIGURE 3 an alternate arrangement for controlling pipes 22 is shown. As in the preceding arrangement, the pipes are mounted on chamber 21 and communicate therewith through passageways 22a controlled by sliders 23. On the wind chest 20 which adjoins chamber 21 there is provided actuator 14, with pole piece 14a and armature 14b, the actuator being secured to a bracket 15 and the armature being pivoted thereto by means of pin 16. Bracket 15 is secured by screws 15a or other suitable means to the chest 20. A restoring spring 18 coupled between the armature and the bracket provides the means for returning the armature to its deenergized position. The chest 20 in its interior includes an organ pouch 24. The diaphragm section of the pouch has at tached thereto a valve 2%, adapted to open and close a port 29 between the wind chest 20 and pipe chamber 21,. when the pouch is collapsed and expanded. Control over the pouch is provided by a valve 25 secured to a lateral extension of armature 14b. In the disengaged position, armature 14b positions valve 25 to close a port 2611 in wind chest 24 which communicates with the atmosphere or with a reduced pressure environment. In this position pneumatic pressure as indicated at P, is coupled into the wind chest 21) proper and also into the interior of pouch 24 through port 26b. Under these conditions, spring 28a in the interior of pouch 24 urges the pouch into its ex-' panded position to thereby position valve 28 into closing engagement with port 29 which provides communication, between the wind chest 20 and the pipe chamber 21.

Upon energization of actuator 14 from the key transducer system, armature 14b is attraced towards pole piece:

14a and, in the fully activated postion, closes port 26b" and opens ports 26a. Under these conditions pouch 24 is externally subjected to pneumatic pressure, P, while the interior is vented to the atmosphere or a reduced pressure (vacuum) through port 26a, now open. This causes the pouch to collapse thus moving valve 28 carried thereon away from port 29 so that the latter is now open and acts to couple pneumatic pressure, P, from wind chest 20 to pipe chamber 21. Pipes 22 are thereby sounded.

When actuator 14 is deenergized, the armature 14b thereof closes port 26a and opens port 26b thereby equalizing the internal and external pouch pressures. Spring 28a then acts to expand the pouch thus closing port 29 and deactivating the pipes 22. The system of control embodied in FIGURE 2 is particularly suitable where a substantial number of pipes have to be controlled.

The arrangement of FIGURE 4 is somewhat similar to the arrangement of FIGURE 3 except that the restoring springs for the actuator and the pouch are eliminated. Thus, in FIGURE 4 armature 14b is restored to its OE position by gravity. In this position, pneumatic pressure, 2P, is coupled through a port 35 in a coupler 36 to the interior of pouch 33 located in wind chest 37. A lesser pressure, P, acts on the exterior of the pouch via port 39 in chest 37. In the presence of the excessive internal pressure the pouch expands and valve 34 carried thereon closes port 29 which, when open, provides communication between pipe chamber 21 and wind chest 37. The pipes are thereby deactivated.

Upon actuation of a key, the associated electro-magnet 14 is actuated and armature 14b is accordingly attracted fully or partially, thereby moving valve 31 attached thereto toward the closing position with respect to port 35. At the same time the valve opens a port 35a thereby venting the interior of pouch 33 to the atmosphere or a reduced pressure (vacuum). Since external pressure, P, is applied to the pouch via port 39 the latter collapses, exhausting its contents to the atmosphere or reduced pressure environment through ports 32 and 35a. As the pouch collapses, valve 34 carried thereon opens port 29, thus supplying pressure to pipe chamber 38 from chest 37 and causing the pipes to sound.

Position control over the pipe valves of FIGURES 3 and 4 is attained because the intermediate pneumatic amplifiers 24, 33 are multistable, i.e., have more than two stable states. Intermediate points of equilibrium exist due to pressure drops occurring across the partially opened and closed valves when the actuator is partially energized. Thus, a partial displacement of a key will result in partial actuation of the associated pneumatic amplifier and valve, while a more complete displacement will result in a more complete actuation of the amplifier and valve operated thereby.

Various embodiments of the key transducer system are illustrated in FIGURES 5 to 9, each embodiment serving to convert key displacements into related electrical signals. In FIGURE 5, key It) carries at its rear a horizontally extending lever 50 and is spring-loaded into its rest position by spring 51 connected at one end to lever 50 at the junction of the bracket and key and at its other end to the frame of the instrument. Attached to the extended end of lever Si) is movable contact 53 of rheostat 52. One end of the rheostat is energized from an electrical source V while the movable contact 53 is connected to the electromagnet 14 (not shown) or other suitable actuator via lead 54. Displacements of key 19 cause corresponding movement of contact 53, thus decreasing the effective resistance introduced into the circuit by rheostat 52. As key is depressed, successively increasing resistance is removed from the circuit between the source V and the pipe actuator so that the current fed thereto increases with increasing key depression. In view of the effectively nonlinear load presented to the pipe actuator, the resistance distribution of rheostat 52 may be conveniently nonlinear to compensate for these non-linearities in the actuator mechanism. For example, the resistance distribution of rheostat 52 may be adjusted to provide an initially large decrease in resistance to overcome threshold pressure-loading of the pipe valves actuated by the electromagnetic actuator, while subsequent changes in resistance *of rheostat 52 may be less marked to conform with the decreasing load requirements placed on the actuator. (An alternate or complementary technique for supplying this 6 feature is provided by the shaping of the magnetic circuit of the actuator as previously described.)

An arrangement somewhat analogous to that of FIG- URE 5 is shown in FIGURE 6. While the circuit of the two is the same, the type of rheostat differs. Thus, in FIGURE 6 a roller 61 is rotatably mounted on the remote end of horizontal lever 60 resting on the rear of key 10. This roller engages one side of conductive spring 62, the other side of which engages the resistance element 63. The latter is energized from source V. Depressions of the key 10 cause roller 61 to urge a successively greater length of spring 62 against resistance element 63, thereby progressively reducing the resistance in the circuit such that current flowing from source V, through resistance 63, and conductor 62, to the pipe actuator via lead 64, increases with increasing key displacements. As in the case of FIGURE 5, resistance element 63 may, if desired, be made non-linear to conform with non-linear characteristics in the output circuit. Moreover, both circuits may employ potentiometer type connections if the actuator requirements so dictate this arrangement.

A key transducer which does not require physical contact between the key 10 and the variable electrical elements of the transducer system is shown in FIGURE 7 where an oscillator is coupled to a transistor 77 by way of a series tuned circuit 75. The collector of transistor 77 is connected to a supply terminal B while the emitter thereof is connected via resistance 78 to a return or ground point. The tuned circuit comprises the series connection of a capacitor 72 and an inductor 74-. Capacitor 72 consists of a pair of plates 71a and 7112, the former being mounted on a bracket 70 suitably insulated. The bracket 74 is secured, in turn, at one end to the rear of key 10 and at its other end to a core 73 which cooperates With inductor '74. With this arrangement movements of key 10 modify the value of capacitor 72 and inductor 74. As the key is depressed plates 71a and 7112 move closer together to increase the capacity of capacitor 72. As the key is depressed the positioning of core 73 further within the inductor winding 74 also occurs, causing the inductance of this element to increase. (Where design considerations so dictate, core 7 3 may be made of a conductive non-magnetic material, in which event displacements cause a decrease in the inductance of coil 7 4.)

With the key in its rest position, the circuit dimensions are so chosen that the circuit 75 is de-tuned with respect to the oscillator frequency. As the key is depressed circuit 75 approaches the resonant condition and the circuit impedance accordingly decreases. Attending this decrease in impedance is an increase in the current fed from the oscillator to the base of transistor 77. Half-wave rectification provided by rectifier 76 also connected to the base, together with the efiective inductance of magnet 14 serves to convert the controlled oscillator output into a substantially single polarity (D.C.) signal, which signal energizes the actuator via transistor output circuit 79. Increasing key displacements cause a correspondingly greater current to be coupled from the oscillator to the actuator via the series circuit 75 and transistor 77, thus providing for increased actuation of the sound source controlled by electro-magnet 14. It may be seen in FIG- URE 7 that there is no physical contact between the key 10 and the transducer circuit.

Another contactless method of transducing key displacements is illustrated in FIGURE 8. In this arrangement a photoelectric technique is provided with a source of radiant energy being provided by lamp 81 energized from electrical source S. Lamp 81 is preferably of the incandescent type and may be of the Lumiline type so thta it can be arranged across the keyboard to serve as a common light source for the systems associated with all the keys. With key 10 in its normal rest position, the radiant energy emitted from lamp 81 is obstructed, and thereby prevented, from impinging on a photosensitive element 83 which may comprise, for example, a photoconductive cell of the cadmium sulfide type connected to an output circuit 84. This shielding is accomplished by a shade 86 integral with a bracket 80 riding on the rear of key 10. Also connected to this bracket and to the frame of the instrument is a spring 85 for urging the key into its rest position. Screen 86 is provided with an aperture 82 which may be rectangular or of other shape to control the radiation of photosensitive element 83 from source 81. As the key 10 is depressed, a successively increasing amount of radiation passes through aperture 82, in a manner dependent on the shape and size of the aperture, from source 81 to the photoconductive cell thereby causing a concomitant increase in the current generated by the cell and delivered to the electro-magnet or other actuator for the instrument sound source. The photoconductive cell 83 has suflicient output when properly radiated according to the arrangement of FIGURE 8 for providing suflicient energizing current for the actuator so that no intermediate amplifier is required. This current is responsive in amplitude and slope, to the displacement and rate of displacement of the key 10.

The systems described heretofore provide the organist with control over the transient response of the pipes, this being accomplished in part by employing continuously variable key transducer systems and a continuously variable actuator such as electro-magnet 14. A system which provides the organist with transient control without the need for a continuously variable transducer and actuator is shown in FIGURE 9. In this system key 10 engages a lever 100 resting on the rear of the key. Also connected to this lever is a spring 193, the other end of which connects to the frame 104 of the instrument. The lever at its remote end carries a striker head 105 pivotally coupled thereto by pin 106. Striker head 105 is adapted to engage springs 107 of a switch 108, the springs being mounted in a terminal block 108a thereof. As key It) is depressed, lever 100 is rotated on pivot 191 and striker head 105 thus moves downward thereby compressing springs 107. After a predetermined initial displacement springs 107a and 1071) make contact, this action serving to complete a circuit to solenoid 110 as more fully described hereinafter. Further displacements of key 10 cause contacts 107a and 107k to contact spring 1070 and thereafter spring 107d. As these latter springs are contacted additional circuits are completed to solenoid 110, causing further actuation thereof.

Solenoid 110 is equipped with a plurality of windings 111, having respective terminals el -a 61 -61 and a -a One side, a a and a of each Winding of solenoid 11a is connected to the positive terminal of source 109. The other terminals of each winding are connected to respective springs of switch 108. Spring 107a of the switch is connected to the negative terminal of source 109. From this circuit arrangement it may be seen that the closing of contacts 107a and 107b completes a circuit between source 109 and winding a a of solenoid 11th As actuation of key continues, spring 1070 is contacted, thereby further energizing solenoid 119 via winding a -a Upon further depression of key 10, spring 107d is alsocontacted, thus completely energizing solenoid 110 through energization of additional winding rig-a As the energization of solenoid 110 progressively increases as described above, axial plunger 112 of the solenoid moves progressively further into the core. Connected to the plunger is a cable 113, the other end of which is connected to a rocker 114 pivoted at 114'. The remote end of rocker 114 is connected to pallet 116 via cable 115. The pallet is normally urged into the closed position by a spring 119. All of this structure including solenoid 114 is located in wind chest 118 which is energized by pneumatic pressure. As solenoid 110 is energized, pallet 116 is pulled into the open position thus opening port 121 which provides communication between wind chest 118 and pipe chamber 120. Thus, depression of key 10 causes pipes 122 connected to pipe chamber 120, to sound, and the transient activation and decay of these pipes is controlled because the degree and rate of opening of port 121 is controlled according to the degree and rate of actuation of key It) by the organist.

An additional feature of the invention relates to the emploment of the restoring spring; e.g., 51, FIGURES 5, 6; 85, FIGURE 8; 103, FIGURE 9, for biasing the key into its rest position. The springs employed are angularly arranged with respect to the key action so that a toggle-like effect is obtained whereby a momentarily high pressure is encountered when initially displacing the key, while reduced pressure occurs once the key has been initially displaced. In some of these figures the angle between the key and lever has been exaggerated to prevent the obscuring of details.

It is to be understood that the various pipe actuators of FIGURES 1 to 4 and 9 may be conventionally combined with any of the transducer systems of FIGURES 5 to 9 to provide combinations most suitable to the requirements of a particular instrument. Moreover, the components of the invention may be modified in arrangement, e.g., by locating each electro-magnetic actuators beneath its associated pipe, without departing from the primary characteristics of the invention. It should also be understood that the invention contemplates a plurality of each of the control systems, one being associated with each key-pipe combination so that the instrument is completely controlled.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and Without sacrificing its chief advantages.

In the accompanying claims, a reference to player contemplates both animate operators and inanimate activating devices for operating the musical instrument.

What is claimed is:

l. A pipe organ having movable playing keys and tone producing pipes corresponding to said playing keys, each pipe having a valve for controlling the speaking of said pipe and the amplitude of sound produced by said pipe, an electro-mechanical transducer means connected to each playing key for producing an electrical signal with a property directly proportional in value to the extent of displacement of said key for at least three diflerent displacements thereof, an electro-mechanical operating means connected to the control valve of each pipe for controlling the extent of opening of said valve in direct proportion to the value of a property of an electrical signal applied to said electro-mechanical operating means, and a plurality of electrical circuits connecting the electro-mechanical transducer means of respective playing keys to the electro-mechanical control valve operating means of corresponding pipes.

2. Apparatus according to claim 1, in which the electro-mechanical operating means includes an electro-magnet which positions the control valve.

3. Apparatus according to claim 1, in which said electro-mechanical transducer means comprise a variable electrical element the impedance of which is adjusted according to said displacements.

4. Apparatus according to claim 1, in which said electro-mechanical transducer means comprise rheostat means including an adjustable contactor which is actuated according to said displacements.

5. Apparatus according to claim 1, in which said electro-mechanical transducer means comprise tunable circuit means including a reactance variable according to said displacements.

6. Apparatus according to claim 1, in which said electro-mechanical transducer means comprise photo-electric means including radiant energy sensing means for producing said electrical signal and optical means responsive to said displacements for controlling the actuation of said sensing means.

7. Apparatus according to claim 1, in which said electro-mechanical operating means comprise electro-magnetic means adapted to provide controllable displacements for actuating said pipe.

8. Apparatus according to claim 1, in which said electro-mechanical operating means includes a plurality of pneumatically coupled valves, one of which is operable to directly control the actuation of said pipe.

9. Apparatus according to claim 1, in which said electro-mech-anical operating means includes a pneumatic amplifier and an electro-magnet for controlling said amplifier, the output motion of said amplifier being coupled to the control valve for causing said valve to control the actuation of the pipe.

References Cited in the file of this patent UNITED STATES PATENTS Hope-J ones July 3, Breed Jan. 28, Skinner Oct. 21, Hope-Jones Ian. 21, McMurtry Aug. 19, Compton Oct. 16, Hammond Aug. 7, Spielmann Oct. 14, Hallman Dec. 4, Reisner Apr. 14, Bowman Aug. 18,

FOREIGN PATENTS Great Britain Great Britain Germany June 3, Great Britain Jan. 10, 

1. A PIPE ORGAN HAVING MOVABLE PLAYING KEYS AND TONE PRODUCING PIPES CORRESPONDING TO SAID PLAYING KEYS, EACH PIPE HAVING A VALVE FOR CONTROLLING THE SPEAKING OF SAID PIPE AND THE AMPLITUDE OF SOUND PRODUCED BY SAID PIPE, AN ELECTRO-MECHANICAL TRANSDUCER MEANS CONNECTED TO EACH PLAYING KEY FOR PRODUCING AN ELECTRICAL SIGNAL WITH A PROPERTY DIRECTLY PROPORTIONAL IN VALUE TO THE EXTENT OF DISPLACEMENT OF SAID KEY FOR AT LEAST THREE DIFFERENT DISPLACEMENTS THEREOF, AN ELECTRO-MECHANICAL OPERATING MEANS CONNECTED TO THE CONTROL VALVE OF EACH PIPE FOR CONTROLLING THE EXTENT OF OPENING OF SAID VALVE IN DIRECT PROPORTION TO THE VALUE OF A PROPERTY OF AN ELECTRICAL SIGNAL APPLIED TO SAID ELECTRO-MECHANICAL OPERATING MEANS, AND A PLURALITY OF ELECTRICAL CIRCUITS CONNECTING THE ELECTRO-MECHANICAL TRANSDUCER MEANS OF RESPECTIVE PLAYING KEYS TO THE ELECTRO-MECHANICAL CONTROL VALVE OPERATING MEANS OF CORRESPONDING PIPES. 